Multiple eigenmode analysis and density jumps in planar surface-wave plasmas with slot-antenna excitation

Electromagnetic surface waves excitation in cold overdense uniform planar plasma is modeled and numerically analyzed. The microwave is injected through a slot antenna cut in the wall of the metal vessel and the forced electromagnetic oscillation localized in the slot is expanded in a series of eigenmodes, which propagate through a dielectric plate into the plasma. A general formulation for arbitrary plasma cross section and slot aperture geometry is given. It provides the basis for optimizing the slot-antenna design. The general approach is analytically applied to a large-area planar cylindrical plasma excited by an annular slot. Numerical results on the relative intensities of the individual eigenmodes and the overall field distribution at the plasma-dielectric interface for various electron densities are reported. The computed density dependence of the power reflection coefficient is shown to lead to density jumps and power-density hysteresis loops corresponding to the experimentally observed behavior.